Terry A. McCormick

Test-Retest Variability of Topographic Measurements With Confocal Scanning Laser Tomography in Patients With Glaucoma and Control Subjects

Using confocal scanning laser tomography, we studied the test-retest variability of topographic measurements of the optic nerve head and parapapillary retina in 30 patients with glaucoma and 30 normal control subjects. We obtained three independent images, separated by between one and six hours, centered on the optic nerve head. We condensed each original 256 x 256-pixel image to a 64 x 64-pixel image, thereby allowing a realistic estimate of the empiric 90% confidence interval of testretest variability at each condensed pixel. Confidence interval maps generated for each subject showed highest measurement variability along the cup border and blood vessels. The mean standard deviation equivalents of test-retest variability in the patients and controls were 31.20 and 25.94 microns, respectively. These differences were statistically significant (P = .010). Variability increased with age (P < .001). When the analysis was repeated for discrete parapapillary areas, the group differences were not statistically significant (P = .100).

Comprehension of concrete and abstract words in autistic children

This study employed the Stroop paradigm to examine comprehension of single words in autistic children. The words of interest varied along a concrete-abstract dimension. In the Stroop paradigm, subjects are asked to name the color of ink in which color words are printed. Comprehension is indexed by the degree to which the automatic processing of words interferes with the colornaming task. For both concrete and abstract words, autistic children showed the same degree of interference as readingmatched controls. The findings corroborate and extend previous work suggesting that autistic children understand, and by implication, can mentally represent, at least some word meanings.

Intraocular pressure and progression of glaucomatous visual field loss

PURPOSE To evaluate the relationship between intraocular pressure and visual field progression in patients with primary open-angle glaucoma. METHODS We prospectively followed 113 patients with early to moderate glaucomatous field damage. Conventional automated static perimetry, high-pass resolution perimetry, and intraocular pressure measurements were carried out at 6-month intervals. The mean and the highest intraocular pressure in the follow-up were compared in stable and progressing patients with each perimetric technique. RESULTS The mean (+/- SD) follow-up was 4.5 +/- 0.9 years. The mean (+/- SD) intraocular pressure in patients remaining stable with conventional perimetry [18.2 +/- 3.3 mm Hg, n = 81 (71.7%)] was not significantly different (P =.65) from those in whom it progressed (17.9 +/- 3.3 mm Hg, n = 32 [28.3%]). The mean intraocular pressure in patients remaining stable with high-pass resolution perimetry (17. 9 +/- 3.5 mm Hg, n = 63 [55.8%]) was not significantly different (P =.33) from those in whom it progressed (18.5 +/- 3.0 mm Hg, n = 50 [44.2%]). The mean (+/- SD) of the highest (single or three highest) pressure during follow-up for stable and progressing patients with conventional perimetry was not significantly different (22.6 +/- 5.0 and 23.0 +/- 4.6 mm Hg, respectively, P =.76). However, for high-pass resolution perimetry, the difference was highly significant (21.6 +/- 4.5 and 24.1 +/- 4.9 mm Hg, respectively, P <. 01). Furthermore, patients who progressed with high-pass resolution perimetry had more damaged baseline fields compared with those who remained stable (P <.01). CONCLUSIONS The mean level of intraocular pressure does not differentiate glaucoma patients with progressive visual field loss from ones who remained stable. Baseline visual field status and peak intraocular pressure of patients who progress with high-pass resolution perimetry are significantly different from those who remain stable.

Visual field and optic disc progression in patients with different types of optic disc damage: A longitudinal prospective study

OBJECTIVE To evaluate the incidence of visual field and optic disc progression in glaucoma patients with distinct patterns of optic disc damage. DESIGN Prospective, observational case series. PARTICIPANTS One hundred five patients with open-angle glaucoma. METHODS Baseline optic disc photographs of 105 study eyes of 105 patients were reviewed by 2 masked observers and classified according to patterns of disc damage into the following categories: focal, myopic, senile sclerotic, and generalized disc damage. Patients were followed up every 6 months with standard automated perimetry (SAP), high-pass resolution perimetry (HRP), and scanning laser tomography (SLT) with the Heidelberg Retina Tomograph. MAIN OUTCOME MEASURES Visual field (SAP and HRP) and optic disc (SLT) progression were determined according to predefined criteria. RESULTS Twenty-four eyes were classified into the focal, 8 into the myopic, 12 into the senile sclerotic, and 28 into the generalized group. Eyes from 33 patients could not be classified by the observers into any of these groups and were excluded from further analysis. Although intraocular pressure during follow-up was similar among the four groups, some differences in frequency of progression were observed. Patients with senile sclerotic discs had the lowest rates of visual field progression (both with SAP and HRP) and optic disc progression, although the differences were significant only for optic disc progression (P = 0.05). CONCLUSIONS Patients with senile sclerotic discs showed a tendency towards less visual field and optic disc progression when compared with patients with other types of disc damage.

Effect of the cardiac cycle on topographic measurements using confocal scanning laser tomography

Abstract• Background: This study was carried out to investigate the effect of the cardiac cycle on topographic measurements of the optic nerve head and peripapillary retina with confocal scanning laser tomography. • Methods: The sample comprised 25 healthy subjects (mean age 40.44 years, range 23–67 years). Using a random crossover design, we obtained a set of three images using the Heidelberg Retina Tomograph (Heidelberg Engineering GmbH, Heidelberg, Germany) under each of two conditions. In the first, the images were obtained normally, while in the second, image acquisition was pulsesynchronised using an electrocardiographic signal. We compared the variability of topographic measurements under the two conditions in the whole image, in the optic nerve head and in the peripapillary retina free of visible vessels. • Results: Nineteen subjects (76%) showed a decrease in variability in the whole image under the pulse-synchronised condition. The respective numbers for the optic nerve head and peripapillary retina were 20 (80%) and 21 (84%). The decrease in variability ranged widely, with a mean of 13.62% in the whole image, 12.26% in the optic nerve head and 18.51% in the peripapillary retina. These decreases were highly significant. There was no relationship between the decrease in variability and age, intraocular pressure, blood pressure, heart rate or the area of the image occupied by blood vessels. • Conclusion: Detecting structural change depends on the accurate assessment of each subjects variability. Because the cardiac cycle confounds this assessment by varying and unpredictable amounts, it may be necessary to obtain pulse-synchronised images routinely.

Agreement among clinicians in the recognition of patterns of optic disk damage in glaucoma.

PURPOSE To determine the interobserver and intraobserver agreement in the recognition of different patterns of glaucomatous optic disk damage and evaluate if these patterns changed over time in patients followed for a number of years. METHODS Patients with early to moderate glaucoma (n = 105) were consecutively enrolled to participate in a prospective observational study. In the first part of the present study, optic disk photographs obtained closest to patients entry date in the prospective study were classified in a masked fashion by three observers according to the pattern of optic disk damage into one of the following: (1) focal, (2) myopic, (3) senile sclerotic, (4) concentric cup enlargement, (5) normal appearance, or (6) miscellaneous (those disks that did not qualify for any of the other groups). The observers were also asked to assign a confidence score for each classification, ranging from 1 (low confidence) to 5 (highest confidence). The three observers reclassified the photographs after a minimal period of 2 months, in order to assess intraobserver agreement. In a second part of the study, one observer reviewed, in a masked fashion, all the optic disk photographs that had been taken during the routine follow-up of the 105 patients in order to evaluate whether the classification of disk pattern changed over time. RESULTS Intraobserver agreement yielded kappa values (95% confidence interval [CI]) from 0.51 (CI, 0.40 to 0.62) to 0.85 (CI, 0.77 to 0.93) depending on the observer. Interobserver agreement kappa values between all three observers was 0.40 (CI, 0.35 to 0.46), but it improved if photographs classified with moderate or higher degrees of confidence were included (0.52 [CI, 0.44 to 0.60]). During a mean follow-up period of 8.2 +/- 4.8 years, 41.6% of the eyes were always classified into the same group and 23.6% of the eyes were classified at least once into two or more of the four patterns of damage (groups 1 to 4). CONCLUSIONS Intraobserver agreement on the pattern of optic disk damage was generally very good, with some variation among the observers. Interobserver agreement was reasonable and increased proportionally with the confidence in the classification. During long-term follow-up, the pattern of optic disk damage usually did not change. This type of classification can probably be used accurately in clinical practice.

Comparison of Reliability Indices in Conventional and High-pass Resolution Perimetry

PURPOSE The purpose of this study is to compare reliability indices in conventional (Humphrey) and high-pass resolution (Ring) perimetry in healthy subjects followed prospectively at 6-month intervals. METHODS Of the 146 healthy subjects (mean age, 50.24 years; range, 30-84 years) enrolled in the study, 102 have been tested twice and 71 three times. The authors compared the reliability indices, fixation losses, false-positive rate, and false-negative rate between the two techniques, both cross-sectionally and serially. RESULTS Fixation losses were slightly higher with high-pass resolution perimetry, whereas false-positive errors were higher with conventional perimetry. False-negative errors were uncommon with either technique. Of 319 fields, 30 (9.4%) conventional and 39 (12.2%) high-pass resolution perimetry fields were unreliable using the current suggested reliability criteria. Nearly all unreliable fields were due to high fixation errors. Using alternative criteria derived from baseline 95th percentile values, unreliable fields were attributed more equally to all three reliability parameters. In subjects tested three times, the reliability indices remained constant. CONCLUSION The results of this study showed that healthy subjects have comparable reliability indices when tested with conventional and high-pass resolution perimetry.

Retinal arterial diameter changes in progressive and nonprogressive glaucoma.

PurposeTo determine if the degree of retinal arterial diameter change is different between patients with progressive and nonprogressive open-angle glaucoma. Material and MethodsIn this prospective cohort study, 44 eyes of 44 open-angle glaucoma patients (mean age, 67.5 years; age range, 52–84 years; mean follow-up period, 4.9 years; follow-up range, 1.3–7.5 years) were included. The change in arterial diameter between the baseline and the most recent follow-up optic disc photograph was determined. The diameter of the 4 major arteries was measured at the optic disc margin and at the thinnest and broadest locations within 1 optic disc diameter from the disc margin. Patients were stratified into progressing and nonprogressing groups according to visual field and optic disc criteria. ResultsVisual field progression was observed in 13 (30%) patients and optic disc progression in 24 (55%) patients. On average, the arterial diameters at the edge of the optic disc decreased significantly by 2.37% (95% CI, −3.31% to −1.41%) per year of follow-up (P <0.001). No significant difference in generalized or focal arterial narrowing was observed between progressive and nonprogressive groups regardless of the criterion used (P >0.462). With this sample, the power to detect a 10% difference in arterial narrowing between the 2 groups was 66%. There was no relationship between the rates of visual field progression and arterial diameter change in the whole group (P = 0.171) or in groups segregated into progressing and nonprogressing patients (P >0.104). ConclusionArterial diameters decreased in both progressive and nonprogressive glaucoma. In this study, there was little evidence that arterial narrowing was more pronounced in progressive disease.

Intra- and interrater agreement with cumulative defect curves.

Purpose:To examine intra- and interrater agreement when analyzing cumulative defect curves. Cumulative defect (Bebié) curves provide a graphical representation of the visual field and allow a subjective classification of diffuse and localized loss. Methods:We used 75 Humphrey 30–2 visual field tests, randomly chosen from a database of 782 fields of 113 patients with open-angle glaucoma. Cumulative defect curves were generated and randomly arranged into five sets, with each set containing the 75 curves in a unique sequence. Five raters (two experienced and three inexperienced) rated each set and classified each curve as showing diffuse loss, localized loss, both diffuse and localized loss, or no loss. The intra-and interrater agreement in rating the curves was then analyzed. Results:Intrarater agreement ranged from 73.3–88.0% for perfect rater agreement, with 5 identical ratings. Agreement for experienced versus inexperienced raters gave similar results (means: 84.0% and 77.8%, respectively, for perfect agreement). Interrater agreement for each set, evaluated by the kappa statistic, was substantial for all 5 sets (0.65–0.71). Kappa values for each set were comparable for experienced and inexperienced raters (0.72–0.83 and 0.59–0.69 respectively). Conclusions:Analyzing the nature of visual field loss using the cumulative defect curve is simple to learn and provides high intrarater agreement as well as substantial interrater agreement.